Various types of conductive material layers may be employed in semiconductor devices. The conductive material layers may be formed using known techniques, such as a physical vapor deposition (PVD) technique or a chemical vapor deposition (CVD) technique. The conductive material layers may be patterned to form interconnection lines for connecting discrete devices with each other on a semiconductor substrate. The interconnection lines may be formed of metal layer(s) having low resistivity in order to enhance the transmission speed of the electrical signals. However, the interconnection lines may also include additional conductive material layers called“barrier metal layers,” which can reduce junction spiking phenomenon.
The barrier metal layer can be formed in a gap region such as a contact hole or a via hole or in another area having a high aspect ratio. The barrier metal layer may be conformably formed in the gap region. The barrier metal layer can be formed after the formation of transistors or capacitors. Thus, in order to reduce the degradation of the electrical characteristics of the transistors and capacitors, it may be advantageous to form the barrier metal layer at a relatively low temperature. For example, when the barrier metal layer is formed after formation of an aluminum layer, the barrier metal layer may be formed at a lower temperature than the melting point of the aluminum to reduce degradation of the aluminum. It may also be advantageous to form the barrier metal layer at a low temperature with good step coverage.
The barrier metal layer may be formed using the PVD technique, which may also be referred to as a sputtering technique. However, the PVD technique may exhibit poor step coverage. Thus, a barrier metal layer formed by the PVD technique may not adequately conform to a gap region having a high aspect ratio. Therefore, a chemical vapor deposition (CVD) technique has been proposed to form a conformal barrier metal layer. However, the CVD technique may require deposition temperatures that can be high compared to the temperatures used in the PVD technique. A metal organic chemical vapor deposition (MOCVD) technique can also be used in the formation of the barrier metal layer because the MOCVD technique may provide good step coverage at a low processing temperature.
FIG. 1 is a flow chart illustrating operations according to a conventional MOCVD method of forming a metal interconnection layer.
Referring to FIG. 1, a semiconductor substrate can be loaded into a first chamber (step S1). A barrier metal layer can be formed on the semiconductor substrate in the first chamber (step S2). The barrier metal layer can be formed using a metal organic precursor. Thus, the barrier metal layer may contain carbon atoms. In this case, the barrier metal layer may have a plurality of pores therein. The semiconductor substrate having the barrier metal layer may be unloaded from the first chamber (step S3). After the semiconductor substrate has been unloaded from the first chamber, it can be exposed to air containing oxygen when the wafer is stored, for example, in a wafer storage box until it is needed in the next process step (step S4). The oxygen may penetrate into the porous barrier metal layer, which can result in an increase of the electrical resistance of the barrier metal layer.
The semiconductor substrate in the wafer storage box can be loaded into a second chamber (step S5). An upper metal layer may be formed on the barrier metal layer (step S6). The substrate having the upper metal layer formed thereon can be unloaded from the second chamber (step S7).
As discussed above, the conventional MOCVD technique may lead to an increase in the electrical resistance of the barrier metal layer due to oxygen and/or carbon contamination. Thus, various additional preventive processes may be carried out prior to formation of the upper metal layer. For example, a plasma treatment may be performed to remove the carbon, and/or a degassing process may be performed to remove the oxygen. However, the plasma treatment may not effectively remove carbon from the barrier metal layer if, for example, the barrier metal layer is conformably formed in a gap region that has a high aspect ratio. Also, the degassing process may be performed at a high temperature in order to remove the oxygen in the barrier metal layer. Accordingly, degradation to other substrate layers can occur and/or resistivity of the metal layers may be increased, which can adversely effect the reliability of the barrier metal layer.